Electric circuit and a safety switch therefor



Dec. 20, 1949 J. P. WALL 2,492,077

ELECTRIC CIRCUIT AND A SAFETY SWITCH THEREFOR Filed Oct. 18, 1947 IN V EN TOR.

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Patented Dec. 20, 1949 UNITED STATES PATENT OEFlCiFl ELECTRIC CIRCUIT AND A SAFETY SWITCH THEREFOR John P. Wall, Los Angeles, Calif.

Application October 18, 1947, Serial N 0. 780,631

1 Claim. 1 This invention relates to electrical apparatus and particularly pertains to an electric circuit and a safety switch therefor.

In the operation of various pieces of equipment where electric energy is utilized it often occurs that pieces of electrical apparatus requiring electric energy for their operation are disposed at a remote point from the source of electric energy. This increases the hazard that a short circuit might be created at some point between the source of electric energy and an electric device to be connected therewith. In most instances an electric circuit is controlled by a switch disposed in relatively close proximity to the device to which the electric energy is fed and thus all of the electrical conduits between the switch and the source of electric energy are live and provide conditions whereby a short circuit might be created easily with disastrous results. An example of such a condition is in connection with the starting motor circuit of an internal combustion engine. In such circuits one live feed wire is provided to extend between one pole of the source of energy and one pole of the starting motor while the other pole of the source of electric energy and the other pole of the starting motor are connected to ground wires. thus be seen that at any point along the feed wire where the insulation might be broken a short circuit might be set up with the rounded parts of the structure, such for example, as the frame of an automobile. It is desirable therefore to interrupt the flow of electricity through the feed wire at a point directly associated with the source or electric energy and it is the principal object of the present invention to provide an electric circuit and a safety switch, which switch will act to completely break the feed conduit circuit at a point close to the source of electric energy by simple and effective means.

The present invention contemplates provision of the source of electric energy and a piece of apparatus to which said energy is supplied, said elements being included in an electric circuit interrupted by a manually controlled switch and an electrically controlled master switch whereby opening of the manually controlled switch will act automatically to permit the master switch to interrupt the circuit at a point in close proximity to the source of electric entrgy.

The invention is illustrated by way of example in the accompanying drawing in which the figure is a view in diagram showing the electric circuit and the pieces of electrical apparatus included therein.

It will,

Referring more particularly to the drawings, it indicates the source of electric energy and is here designated as a storage battery, although it is to be understood that any type of electrical generating means might be used in substitution thereof. When a storage battery is used it may be desirable to connect one pole to a ground wire ii, the opposite end of said wire being suitably grounded. The opposite pole of the battery it is provided with a feed wire i2. This wire leads to a master switch generally indicated at if The master switch is provided with a contact i i with which the conductor 52 is connected electrically. A complementary contact 15 is provided. contact is connected electrically with the conductor it which leads to one pole of an electrical piece of apparatus here diagrammatically indicated as the motor ii. The opposite pole of the motor I! is here shown as provided with a ground wire it which makes a suitable grounr connection. The contacts i4 and it of the master switch [3 may be electrically connected by a contact bar l9. This bar is normally disposed out of engagement with the contacts i and it either by gravity or by a spring 2 3 which acts against the end of a solenoid plunger iii, the opposite end of which plunger is connected to the contact bar I9. A solenoid coil 22 is disposed around the plunger 25 and at one end connects with the conductor i2 through a conductor 23. The opposite end of the solenoid coil 22 is provided with a conductor 24 which leads to a manually operated switch 25. The switch 25 is here shown as being of the locked type, including a lock barrel 26 to receive a key 2i. An actuating member 28 on the barrel may be moved into engagement with the switch blade 25. Ihe end of the conductor 24 is attached to the switch blade 29. When the member 23 engages the switch blade 29 it moves the blade 29 into electrical engagement with a contact (iii. A ground wire 3| is attached to this contact at one end while its opposite end is suitably grounded.

In the operation of the present invention a manually operated switch 25 is normally open so that the switch blade 23 is out of contact with the conductor 38. At this time the contact bar i9 will be out of electrical engagement with the contacts l4 and I5, since the master switch It is biased to stand normally in an open position. When it is desired to close the electric circuit to the motor H a manually operated switch 25 is manipulated through the key and lock barrel 25 to move the element 28 so that it will force the switch blade 29 into electrical engagement with the contact 30. This will complete an electric circuit from the source of electric energy I through the feed wire I2 to the conduit 23 and thence through the solenoid winding 22 to conductor 24. Current will then flow through the switch blade 29 to contact 30 and thence through ground wire 3| to ground. The circuit will then be completed to the source of electric energy I0 from the ground wire II. When this circuit is completed the solenoid coil 22 will be energized and will act upon the plunger 2! to draw the contact bar I9 into electrical engagement with the contacts I4 and I5. from the source of electrical energy will then be completed through the feed wire I2, contact I4,

and then through contact bar I9 to contact I5. The flow 0f current will then continue through feed wire I6 to one pole of the piece of electrical apparatus I1 and then from the other pole of the piece of electrical apparatus I! to the ground 'wire- I8; It will be obvious that control switches in close proximity to the piece of electrical apparatus I"! may be interposed at a point in the length of either of the conductors I6 or I8. Preferably in accordance with common practice, a

conventional starter switch I9 is interposed in the conductor I6.

From the foregoing it will be recognized that by manipulation of the manually controlled switch 25 the master switch may be instantly energized from the source of' energy It to break or establish a feed circuit to the piece of apparatus I1 and toinsure that the conductors I and I8 will not have any electrical connection with the source of electric energy Ill when the 5.

master switch-is opened.

It will thus be seen that by the use of the electric circuit here shown and the safety switch structure that all of the electrical conduits in the apparatus will be out of circuit when the master switch is open to save for the relatively short lengths of feed wire I2 and ground wire I I, thus eliminating a major portion of potential fire hazard in theapparatus when electric energy is not required.

While I have shown the preferred form of my invention it is to be understood that various changes may be made in the combination, construction, and arrangement of parts of the apparatus by those skilled in the art without departing from the spirit of the invention as claimed.

The feed circuit' Having thus described my invention, what I claim and desire to secure by Letters Patent is:

A starting system for automobiles including a storage battery, an electric Starting motor located at a remote point from the storage battery, a solenoid master safety switch located directly adjoining the storage battery and comprising a contact bar, a pair of contacts adapted to be engaged by said contact bar, a solenoid plunger secured to said contact bar, yieldable means acting to normally maintain said contact bar out Of engagement with said pair of contacts, a solenoid coil disposed around the plunger, a very short conductor wire leading from one pole of the storage battery to one contact of the master switch, a starter switch, a wire leading from the other contact of the master switch to one contact of the starter switch, a wire connecing the other contact of the starter switch with one pole of the motor, ground wires connected to the other pole of the storage battery and the other pole of the motor, a key-operated lock switch located at a point remote from the master switch, a wire leading from the first mentlcned pole of the storage battery connected to one end of the solenoid coil, a wire leading from. the other end of the solenoid coil to said heyoperated switch, and a ground Wire connected to said key-operated switch, whereby the closing of said key-operated switchv will cause the solenoid to be energized and the master switch to be closed, thereby making the electrical energy from the battery available at the starter switch,

and when the key-operated switch is opened the master switch is automatically opened and dis connects the battery from the starter switch.

JOHN P. WALL.

REFERENCES CITED The following references are of. record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,244,926 Wallace Oct, 30, 1917 1,935,509 Leeah et a1 Novhl l, 1933 1,995,946 Schild Mar. 26, 1935- 2,044,917 Richardson June 23, 1936 2,073,645 Maurer Mar, 16,1937 2,324,844 Hutt July 20, 1943 2,330,505 Matthias Sept..28, 1943. 

